Tirzepatide
Dual GLP-1 / GIP Receptor Agonist
What is Tirzepatide?
Tirzepatide is a synthetic peptide that acts as a dual agonist at both GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) receptors — the two primary incretin hormones that regulate insulin secretion, appetite, and metabolic rate. It is the first approved dual incretin receptor agonist.
GLP-1 receptor agonism reduces appetite, slows gastric emptying, and stimulates insulin secretion. GIP receptor agonism adds complementary effects: improved fat metabolism, reduced inflammation, and enhanced GLP-1 receptor expression — which may explain why tirzepatide outperforms semaglutide (a GLP-1 only agonist) in head-to-head comparisons.
Approved as Mounjaro for type 2 diabetes (2022) and Zepbound for chronic weight management (2023), tirzepatide represents the current gold standard in pharmacological weight loss — with the highest efficacy of any approved drug in its class.
Research Evidence
22.5% average body weight reduction at 15 mg/week over 72 weeks vs 2.4% placebo. ~1 in 3 participants lost ≥25% body weight — a result previously seen only with bariatric surgery.
HbA1c reduction of 2.0–2.3% at maximum dose across multiple Phase 3 RCTs. Superior to insulin degludec, semaglutide 1 mg, and dulaglutide in head-to-head trials.
Significant reduction in major adverse cardiovascular events in obese/overweight adults without diabetes. Phase 3 data supporting cardiovascular benefit class label.
~25–40% of weight lost is lean mass — similar to other GLP-1 agonists. Active resistance training and adequate protein intake significantly preserve muscle. This is the primary clinical concern with long-term GLP-1 use.
Dosing Titration Schedule
Always start at 2.5 mg and titrate slowly. GI side effects (nausea, vomiting) are the primary tolerability issue — slow titration significantly reduces discontinuation rates.
| Weeks | Dose | Notes |
|---|---|---|
| 1–4 | 2.5 mg/wk | Starting dose — always begin here |
| 5–8 | 5 mg/wk | First increase; most GI symptoms resolve by this point |
| 9–12 | 7.5 mg/wk | Optional — skip if tolerating well |
| 13–16 | 10 mg/wk | Most patients see significant weight loss here |
| 17–20 | 12.5 mg/wk | Optional step |
| 21+ | 15 mg/wk | Maximum dose; ~22.5% avg weight loss at this level |
Frequently Asked Questions
What is tirzepatide?
Tirzepatide is a dual GLP-1 and GIP receptor agonist FDA-approved as Mounjaro (T2D) and Zepbound (weight loss). It mimics two incretin hormones simultaneously, reducing appetite and improving metabolic function.
How much weight can you lose on tirzepatide?
The SURMOUNT-1 trial found average weight loss of 22.5% at 15 mg/week over 72 weeks — approximately 52 lbs for a 230 lb person. This exceeds any other approved pharmacotherapy.
What is the tirzepatide titration schedule?
Start at 2.5 mg weekly for 4 weeks. Increase by 2.5 mg every 4 weeks as tolerated up to 15 mg/week maximum. Slow titration dramatically reduces GI side effects.
How does tirzepatide compare to semaglutide?
Head-to-head trial (SURPASS-CVOT) showed tirzepatide produces ~50% more weight loss than semaglutide 1 mg. Direct comparison with semaglutide 2.4 mg (Wegovy) showed 47% greater weight loss favoring tirzepatide. The dual GIP mechanism is believed responsible for the advantage.
This profile was prepared using AI-assisted research synthesis. Citations are provided where applicable — verify with primary sources before clinical application.
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